Consumers want smaller electronic devices that provide more advanced features. Such devices include compact disc players, two-way radios, cellular telephones, and computer devices to name a few. To become smaller, these electronic devices need to use smaller portable energy sources.
Electronic circuits operating at lower voltages reduce the energy consumption of such devices. As a result, a lower operating voltage reduces the size of the portable energy source required to operate an electronic device over a desired period of time. However, some circuits, such as amplifier circuits, operate most efficiently at higher voltages.
Despite low voltage advancements, a portable energy source may be too bulky, too heavy, or may not last long enough for many high power applications. For example, a portable energy source, such as a battery or battery pack, must often deal with short term surges in currents drawn by an electronic device. The battery must be robust enough to provide peak current that may be substantially higher than the average current of the electronic device. Consequently, an electronic device often has a larger battery to meet its power requirements even though a smaller battery would be sufficient for its energy requirements.
To alleviate these problems, an electronic device may be powered by an energy system that includes a capacitor connected in parallel with a battery. Here, the capacitor effectively lowers the impedance of the energy system. During relatively large current pulses, a properly selected capacitor will reduce a voltage drop in the system because of its lower equivalent series resistance. However, the smaller voltage drop associated with these systems is too large for adequate operation in electronic circuits operating at even lower voltages. In such circuits, the voltage drop from the capacitor may cause parts of the electronic device to operate unreliably.
Consequently, there is a need for an electronic means to accommodate these limitations that is suitable for low voltage applications with large current pulse requirements.